<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta content="width=device-width, initial-scale=1.0" name="viewport">
  <title>Document</title>
  <script src="https://unpkg.com/react@18/umd/react.development.js"></script>
  <script src="https://unpkg.com/react-dom@18/umd/react-dom.development.js"></script>

  <!-- Don't use this in production: -->
  <script src="https://unpkg.com/@babel/standalone/babel.min.js"></script>
</head>

<body>
  <div id="root"></div>
  <div id="app"></div>
  <script type="text/babel">

    class APP extends React.Component {
      // 组件数据
      constructor() {
        super()
        this.state = {
          message: 'hello,react'
        }
      }

      //渲染内容 render方法
      render() {
        const { message } = this.state

        const element = <h2>{message}</h2>
        return element
      }
    }

    const root = ReactDOM.createRoot(document.getElementById('root'))
    root.render(<APP />)
  </script>
</body>

</html>